Metformin, the first-line drug to treat type 2 diabetes (T2D), inhibits mitochondrial glycerolphosphate dehydrogenase in the liver to suppress gluconeogenesis. However, the direct target and the underlying mechanisms by which metformin increases glucose uptake in peripheral tissues remain uncharacterized. Lipid phosphatase Src homology 2 domain-containing inositol-5-phosphatase 2 (SHIP2) is upregulated in diabetic rodent models and suppresses insulin signaling by reducing Akt activation, leading to insulin resistance and diminished glucose uptake. Here, we demonstrate that metformin directly binds to and reduces the catalytic activity of the recombinant SHIP2 phosphatase domain in vitro. Metformin inhibits SHIP2 in cultured cells and in skeletal muscle and kidney of db/db mice. In SHIP2-overexpressing myotubes, metformin ameliorates reduced glucose uptake by slowing down glucose transporter 4 endocytosis. SHIP2 overexpression reduces Akt activity and enhances podocyte apoptosis, and both are restored to normal levels by metformin. SHIP2 activity is elevated in glomeruli of patients with T2D receiving nonmetformin medication, but not in patients receiving metformin, compared with people without diabetes. Furthermore, podocyte loss in kidneys of metformin-treated T2D patients is reduced compared with patients receiving nonmetformin medication. Our data unravel a novel molecular mechanism by which metformin enhances glucose uptake and acts renoprotectively by reducing SHIP2 activity.—Polianskyte-Prause, Z., Tolvanen, T. A., Lindfors, S., Dumont, V., Van, M., Wang, H., Dash, S. N., Berg, M., Naams, J.-B., Hautala, L. C., Nisen, H., Mirtti, T., Groop, P.-H., Wähälä, K., Tienari, J., Lehtonen, S. Metformin increases glucose uptake and acts renoprotectively by reducing SHIP2 activity.

The ataxia-telangiectasia-mutated (ATM) kinase is a key transducer of DNA damage signals within the genome maintenance machinery and a tumour suppressor whose germline mutations predispose to familial breast cancer. ATM signalling is constitutively activated in early stages of diverse types of human malignancies and cell culture models in response to oncogene-induced DNA damage providing a barrier against tumour progression. As BRCA1 and BRCA2 are also components of the genome maintenance network and their mutations predispose to breast cancer, we have examined the ATM expression in human breast carcinomas of BRCA1/2 mutation carriers, sporadic cases and familial non-BRCA1/2 patients. Our results show that ATM protein expression is aberrantly reduced more frequently among BRCA1 (33%; P ¼ 0.0003) and BRCA2 (30%; P ¼ 0.0009) tumours than in non-BRCA1/2 tumours (10.7%). Furthermore, the non-BRCA1/2 tumours with reduced ATM expression were more often estrogen receptor (ER) negative (P ¼ 0.0002), progesterone receptor (PR) negative (P ¼ 0.004) and were of higher grade (P ¼ 0.0004). In our series of 1013 non-BRCA1/2 cases, ATM was more commonly deficient (20%; P ¼ 0.0006) and p53 was overabundant (47%; Po0.0000000001) among the difficult-to-treat ER/PR/ ERBB2-triple-negative subset of tumours compared with cases that expressed at least one of these receptors (10 and 16% of aberrant ATM and p53, respectively). We propose a model of 'conditional haploinsufficiency' for BRCA1/2 under conditions of enhanced DNA damage in precancerous lesions resulting in more robust activation and hence increased selection for inactivation or loss of ATM in tumours of BRCA1/2 mutation carriers, with implications for genomic instability and curability of diverse subsets of human breast cancer.

Glycodelin is an endocrine-regulated glycoprotein that has significant effects on immune cells, apoptosis, reproduction, cell adhesion, differentiation and cancer. In reproduction, glycodelin contributes to capacitation and immunoprotection of spermatozoa, and it modulates sperm-oocyte binding, acrosome reaction and implantation. In endocrine-related cancer, the differentiation inducing effects of glycodelin are accompanied by growth restriction of malignant cells, decreased expression of oncogenes, increased expression of tumour suppressor genes and morphological reversion of the malignant phenotype. This review features these properties and clinical connections, highlighting the role of glycosylation in biological actions.

Twenty-four and forty-eight hours after administration of EC, neither the proportion of AR sperm, nor the glycodelin-A level was influenced by 1.5 mg of LNG. LNG did not impair the cervical mucus either because viable spermatozoa were found in the genital tract 36-60 h after coitus and 24-48 h after LNG intake. The mechanism of action of LNG as EC remains unknown.